Radio receiving apparatus



June 9, 1959 w, RQDENHUIS ETAL 2,890,446

RADIO RECEIVING APPARATUS Filed Jan. 7, 1955 INVENTORS WUBE RODENHUIS ANTON MARIE JACOB VAN DER VELDEN BYW AGEN

United States Patent Cfihce 2,890,446 Patented June 9, 1959 RADIO RECEIVING APPARATUS Wijbe Rodenhuis and Anton Marie Jacob van der Velden, Emmasingel, Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc., New York, N.Y., a corporation of Dela= ware Application January 7, 1955, Serial No. 480,518

Claims priority, application Netherlands January 11, 1954 4 Claims. (Cl. 340-384) The present invention relates to radio receiving apparatus. More particularly, the invention relates to radio receiving apparatus including an automatic alarm.

It is known to provide a radio receiving apparatus with a clock having a switching device, by means of which the apparatus may be switched on automatically at particular instants to be chosen arbitrarily by the user.

An apparatus thus constructed may, at the same time, be used as an alarm clock, The signal from a transmitting station, reproduced through the loudspeaker, serves as an alarm signal, which, however, has a disadvantage in that a transmitting station of sufiicient strength cannot always be tuned in during the early hours of day, so that one cannot rely upon the reproduction of an alarm signal during such hours.

The invention has for its object to provide a radio receiving apparatus which can operate reliably as an alarm clock under all conditions. It comprises a device, by which, at a predetermined instant, an alarm signal produced in the apparatus itself is reproduced through the loudspeaker. For this purpose, the apparatus comprises an alarm device or generator for the alarm signal, which is actuated by a switch at the desired instant. As is common practice to do, this may be carried out by means of a clock, more particularly an electric clock. The signal may be supplied directly to the loudspeaker. However, in order to obtain adequate effect, the generator must have a comparatively high power in this case, so that it is to be preferred to feed the signal supplied by the generator to a preceding amplifying stage, which is also used for the reproduction of the normal sound signals. In this case the switch is arranged to be such that it also closes the supply current circuit for the receiving apparatus itself.

According to the invention, the generator may be arranged in a manner such that it produces an alarm signal constituted by a sequence of tap signals. It has been found that such a signal is effective as an alarm signal, while it does not hinder or make too great an alarm. A satisfactory effect is obtained with a comparatively low signal strength. This effect may be enhanced in accordance with the invention, by periodically interrupting the sequence of sound pulses, the alarm signal being thus heard as an interrupted tapping, which has a great stimulating effect.

The frequency of the tapping is preferably about 3 cycles per second and that of the interruption is about 0.4 cycles per second. Each tap may be produced by a single current pulse.

The invention has a further advantage in that, as will be evident from the following description with reference to the drawing, a signal as described above can be produced by very simple means.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein:

Fig. 1 is a schematic diagram of an embodiment of 2 the radio receiving apparatus of the present invention; and

Fig. 2 is a schematic diagram of a signal produced by the alarm device of the present invention.

Referring to Fig. 1, reference numeral 1 designates the resistor in the detector circuit of the radio receiving apparatus. The low-frequency signal occurs across this resistor. The voltage derived from this resistor is amplitied in a low-frequency amplifier comprising two tubes 2 and 3 and is then applied to a loudspeaker 5 through an output transformer 4.

The alarm signal device comprises a parallel combination 6 of a glow-discharge tube, for example a neon tube, and a capacitor; the parallel combination 6 may be connected to a voltage source through a resistor 8.

These elements constitute a known generator for producing relaxation oscillations. The capacitor is charged across the resistor 8 until the ignition voltage of the glowdischarge tube is attained, after which the capacitor discharges abruptly. Then the voltage at the capacitor drops below the ignition voltage of the glow discharge tube and the process is repeated.

Provision is made of a switch 13, which may be closed by a clock at a predetermined, arbitrary instant. The switch 13 is preferably coupled with a switch by means of which the supply current circuit of the receiving section is closed. The left-hand arm of the switch 13 switches on the supply voltage for the generator described, the right-hand arm connects said generator to the input circuit of the first low-frequency amplifying tube 2. This is carried out through a capacitor 10.

The elements of the parallel combination 6 and the resistor 8 are proportioned in such a manner, the voltage of the supply being taken into consideration, that the frequency of the oscillation produced is about 3 cycles per second. After the switch 13 has been switched on, an audible tapping of this frequency is produced in the loudspeaker 5. The alarm device may be such that, after some time, for example a few minutes, the switch 13 is reopened.

In order to obtain the aforesaid interrupted tapping signal, a second parallel combination 7 of a neon tube and a capacitor is provided, it being connected to the supply through a resistor 9. Provision is also made of a common resistor 12. The proportioning of the elements of this second generator for relaxation oscillations is such that in the absence of the first-mentioned generator 6, an oscillation of 0.4 cycles per second would be produced. Due to the presence of a capacitor 11 and the common resistor 12, the generator circuit 7, 9 produces a periodic interruption of the pulse sequence of the generator circuit 6, 8, so that a signal which may be represented by a sequence of peaks as shown in Fig. 2 is produced in the loudspeaker 5. The tapping starts with a lowampli-tude and increases gradually due to the long heating time of the cathodes of the amplifying tubes. By particular measures, which introduce a still greater delay, this effect may be enhanced.

A favorable effect is obtained, if the capacitance of the capacitor of the circuit 6 is about 100,000 micromicrofarads, the resistance of the resistor 8 2.2 megohms, the capacitance of the capacitor of the circuit 7 330,000 micromicrofarads, the resistance of the resistor 9 is 6.8 megohms, and the resistance of the common resistor 12 is 6 megohms. The ignition voltage of the neon tubes is, in this case, about 60 volts at a supply voltage of 200 volts. The capacitors 10 and 11 may have capacitances of 56,000 and 22,000 micromicrofarads. If the generator is in circuit, a normal low-frequency signal can substantially not be amplified.

Instead of using a relaxation oscillation generator of the kind described, other kinds of generators may be used, for example generators comprising controlled vacuum tubes, which produce voltage pulses of similar waveform. The generator described above, however, has the advantage that it is very simple;

If the apparatus is used only for the normal reception, the generator for; the alarm signal is switched off permanently by opening the switch 13 and putting its controldevice out of operation.

While the invention has been described by means of a specific example and in a specific embodiment, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing' from the spirit and scope of the invention.

What is claimed is:

1. Analarm signal generator for use in a radio receiver havinga loudspeaker, comprising a=first relaxation oscillator for producing an electric signal having a substantially low frequency at which tapping sounds are produced, a second relaxation oscillator connected in parallel with said first relaxation oscillator for periodically interrupting said electric signal, and means for coupling the output of saidfirst oscillator to said loudspeaker for predetermined periods of time whereby said loudspeaker produces an alarm signal comprising a regularly interrupted sequence of tapping sounds.

2. An alarm signal generator for use in a radio receiver having a loudspeaker, comprising a first relaxation oscillator for producing an electric signal having a substantially low frequency at which tapping sounds are produced, said first relaxation oscillator comprising a gas discharge tube, a capacitor connected in parallel circuit arrangement with said tube, a first resistor connected at one end to said parallel circuit arrangement, and means for deriving said electric signal from said parallel circuit arrangement, a second relaxation oscillator for periodically interrupting said electric signal, said second relaxation oscillator comprising a second gas discharge tube, a second capacitor connected in parallel circuit arrangement with said second tube, a second resistor connected at one end to said last-mentioned parallel circuit arrange ment, and means for deriving an output signal from said last-mentioned parallel circuit arrangement, common coupling means for intercoupling both said signal deriving means, common connecting means for interconnectingthe other ends of said first and second resistors, a third resistor connected at one end to said common connecting means, a source of supply voltage, and means for simultaneously coupling said common coupling means to said loudspeaker and the other end of said third resistor to said voltage source for predetermined periods of time whereby said loudspeaker produces an alarm signal comprising a regularly interrupted sequence of tapping signals.

3. An alarm signal generator, for use in a radio receiver having a loudspeaker, comprising a first relaxation oscillator for producing an electric signal having a substantially low frequency at which tapping sounds are produced, a second relaxation oscillator connected in parallel with said first relaxation oscillator for periodically interrupting saidelectric signal, each said oscillator comprising a gas discharge tube, a capacitor connected in parallel circuit arrangement with said tube, a resistor connected to said parallel circuit arrangement and means for applying a charging voltage-to said resistor, and means for coupling the output of: said first oscillator to said loudspeaker for predetermined periods of time whereby said loudspeaker produces an alarm signal comprising a regularly interrupted sequence of tapping sounds.

4. An alarm signal generator for use in a radio receiver having a loudspeaker, comprising a first relaxation oscillator for producing an electric signal having a substantially low frequency at which tapping sounds are produced, said first relaxation oscillator comprising a gas discharge tube, a capacitor connected in parallel circuit arrangement with said tube, a first resistor connected at one end to said parallel circuit arrangement, and means for deriving said electric signal from said parallel circuit arrangement, a second relaxation oscillator for periodically interrupting said electric signal, said second relaxation osci lator comprising a second gas discharge tube, a second capacitor connected in parallel circuit arrangement with said second tube, a second resistor connected at one end to said last-mentioned parallel circuit arrangement, and means for deriving an output signal from said last-mentioned parallel circuit arrangement, common coupling means for intercoupling both said signal deriving means, common connecting means for interconnecting the other ends of said first md second resistors, 21 third resistor connected at one end to said common connecting means, a source of supply voltage, and means for simultaneously coupling said common coupling means to said loudspeaker and the other end of said third resistor to saidvoltage source for predetermined periods of time whereby said loudspeaker produces an alarm signal comprising a regularly interrupted sequence of tapping signals, said last-mentioned means comprising an electric clock and a switch operated by said clock.

References Cited in the file of this patent UNITED STATES PATENTS 2,139,023 Kack Dec. 6, 1938 2,140,840 hanger Dec. 20, 193; 2,437,876 Cohn Mar. 16, 1948 2,439,732 Haydon Apr. 13, 1948 2,448,597 Jolley Sept. 7, 1948 2,576,585 Fleming Nov. 26, 1951 2,552,331 Lamb May 8, 1951 2,604,589 Burns July 22, 1952 

